Preparation And Electrochemical Performance Of Li₂FeSiO₄ Films Prepared Using Magnetron Sputtering

As the cathode material,polyanionic silicate series lithium ferrous silicate has the advantages of easy preparation,wide source,high efficiency and green,low cost and high theoretical capacity.In this paper,lithium ferrous silicate（Li₂FeSiO₄）anode films were prepared by RF magnetron sputtering.The effects of RF magnetron sputtering equipment parameters and annealing temperature on the morphology,transport characteristics and electrochemical properties of Li₂FeSiO₄ films were studied.（1）By changing the two main process parameters of sputtering power and sputtering pressure,it is found that when the substrate temperature is normal temperature（25℃）and the sputtering power does not exceed 180W,the prepared Li₂FeSiO₄ film is amorphous,and The growth rate of the film is gradually accelerated with the increase of sputtering power.At the sputtering power of 100W,the particles on the surface of the prepared film were uniform,and the charge conductivity was 3.1746×10^-7 S·cm^-1.When the sputtering pressure was 2Pa,the particles on the film surface were arranged neatly and the charge conductivity was3.5997×10^-7 S·cm^-1.As the sputtering pressure increases,the growth rate of the thin film increases first and then decreases.（2）Under 500℃ annealing conditions,the film began to crystallize,and XRD patterns showed some diffraction peaks of Li₂FeSiO₄.The crystallinity of the films increases with the annealing temperature.After annealing at 900℃,the thin film began to produce impurity peak phases.As the annealing temperature increases,the charge conductivity of the film increases first and then decreases.Among them,the Li₂FeSiO₄ film has the highest conductivity after annealing at 500℃,and the charge conductivity is 4.4707×10^-7 S·cm^-1.（3）The study found that under normal temperature conditions,the sputtering power is100W,and the volt-ampere characteristic curve of the prepared Li₂FeSiO₄ thin film battery shows a pair of obvious redox peaks,mainly corresponding to the redox process of Fe²⁺/Fe³⁺;the discharge capacity of the film in the first cycle It is 129.93mAh/g,and it is cycled to 200times.The discharge capacity of the film is 115.60mAh/g,and the capacity attenuation is less.The corresponding lithium ion diffusion coefficient is up to 1.25×10^-1111 cm²·s^-1.After annealing the Li₂FeSiO₄ thin film at 500℃,two pairs of redox peaks appear on the voltammetric characteristic curve,which correspond to the redox processes of Fe²⁺/Fe³⁺and Fe³⁺/Fe⁴⁺respectively;two pairs of stable voltage platforms appear on the corresponding charge and discharge curves,after 200 times After the charge and discharge cycle,the specific capacity of the battery is 122.11mAh/g,and the capacity retention rate is as high as 92.78%,showing good cycle performance and rate characteristics.The lithium ion diffusion coefficient of the film is 1.22×10^-1111 cm²·s^-1.